Hard crystals such as PLZT (lead lanthanum zirconate titanate) or KTN (Potassium Tantalum Neodymium) are widely used in optoelectronic storage and display devices. The PLZT crystal is a ferroelectric, ceramic, electrooptical material having optical properties which can be changed by an electric field or by being placed in tension or compression.
These crystals are hard but brittle and though they can be cut and polished by conventional ways, it is extremely difficult to shape small 3-D patterns on their surfaces. High powered lasers, such as a carbon dioxide (CO.sub.2) laser, Nd:Yag laser or Excimer laser, can be used. However these conventional lasers have disadvantages. Even because of high absorption, the crystal becomes heated and can reach temperatures close to or even above Curie temperature. These high temperatures cause the loss of the crystal's optical properties, particularly in the region surrounding the processing area.
Copper vapor laser (CVL) are also known in the art of laser etching. In general, the copper vapor laser has an extremely high photon gain and large active aperture. By combining the copper vapor laser with the magnification capabilities of a projection microscope, it is possible to obtain a resolution of one micron. Using very fast pulsed (CVL) the brittle crystal can be "chipped" away or "crumbled" in ordered manner, confined to very small area--without heating. Thus, surface processing, such as etching, drilling and cutting can be performed on a marked area as small as 2 microns.
However, though surface processing can be carried out accurately on extremely small areas, using a projection microscope based on a copper vapor laser, for delicate work on a hard crystal, such as PLZT, it is essential that the crystal be accurately located. The x-y placing of the crystal is especially critical where etching and/or cutting is carried out close to each other.